The LTE (Long Term Evolution), standardized by 3GPP (3rd Generation Partnership Project) which is a standardization organization, is a next-generation system capable of achieving higher-speed and larger-volume communications than the 3rd and 3.5th generation cellular radio communication systems currently in operation.
In the LTE system, a radio base station periodically receives uplink control information from a radio terminal through an uplink control channel (PUCCH: Physical Uplink Control CHannel). The uplink control information includes information (CQI: Channel Quality Indicator) indicating a reception quality of a radio signal received by the radio terminal (that is, a radio quality of a downlink). The uplink control channel employs code division multiplexing using an orthogonal sequence and can multiplex multiple radio terminals by using one frequency resource (RB: Resource Block).
In the LTE system, the radio base station also assigns timing setting parameters and control channel setting parameters to radio terminals connected to the radio base station. The timing setting parameters are provided for determining transmission timing of the uplink control information. The control channel setting parameters are provided for determining the orthogonal sequence used for transmitting the uplink control information. The timing setting parameters as described above are referred to as cqi-pmi-ConfigIndex or ICQI/PMI, while the control channel setting parameters are referred to as cqi-PUCCH-ResourceIndex or n(2)PUCCH (See Non-Patent Literatures 1 and 2).